The Complete Guide to Your Second Trimester (Weeks 13–27)

Welcome to the second trimester — often called the “golden trimester” because, for many women, it’s the most comfortable period of pregnancy. Morning sickness typically fades, energy returns, and you’ll start to feel your baby move for the first time. Between weeks 13 and 27, your baby grows from the size of a peach (7 cm) to nearly 37 cm and develops the ability to hear, see light, and respond to touch.

📌 Key Takeaway: The second trimester (weeks 13–27) is when morning sickness eases, energy returns, and baby’s first movements are felt. The 20-week anatomy scan is the most comprehensive ultrasound of your pregnancy. This is also the ideal time for exercise, travel (babymoon), and glucose screening for gestational diabetes.

Baby Development: Weeks 13–27

Weeks 13–16: Entering the Golden Trimester

Your baby enters the second trimester with all major organs formed — now they mature and grow rapidly.

Week	Size	Weight	Key Developments
13	Peach (7.4 cm)	23 g	Fingerprints forming; vocal cords developing; may start sucking thumb
14	Lemon (8.7 cm)	43 g	Facial expressions developing; palate fully formed
15	Orange (10.1 cm)	70 g	Can sense light through closed eyelids; bones hardening
16	Avocado (11.6 cm)	100 g	Can hear your heartbeat and muffled external sounds

📊 Key Data: Research published in the Proceedings of the National Academy of Sciences shows that fetal hearing develops by 16 weeks, with babies demonstrating measurable heart rate changes in response to sound as early as 24 weeks.

Weeks 17–20: Movement and the Halfway Mark

Between weeks 16 and 20, most first-time moms feel quickening — the first fetal movements. It’s often described as flutters, bubbles, or a gentle tapping. Women who’ve been pregnant before may feel it as early as week 14.

Week 20 is the halfway point. From now on, baby is measured head-to-toe (about 25 cm — the size of a banana). The 20-week anatomy scan happens around this time.

Weeks 21–27: Rapid Growth and Viability

Week	Size	Weight	Key Developments
22	Papaya (27.8 cm)	430 g	Eyes have formed; inner ear developed for balance
24	Corn (30 cm)	600 g	Viability milestone — survival possible with NICU care
26	Lettuce (35.6 cm)	760 g	Eyes open for the first time; brain waves increasingly active
27	Broccoli (36.6 cm)	875 g	Regular sleep-wake cycles; lungs continuing to develop

Week 24 marks the viability milestone. While extremely premature babies face significant challenges, advances in neonatal medicine mean that survival rates at 24 weeks have reached approximately 40–70% in well-equipped NICUs, according to the National Institutes of Health (NIH).

Track your baby’s weekly development with our Week-by-Week Tracker.

The 20-Week Anatomy Scan

The mid-pregnancy anatomy scan (also called the level 2 ultrasound or anomaly scan) is the most detailed ultrasound of your pregnancy. It typically occurs between weeks 18 and 22.

What the Sonographer Checks

Structure	What They’re Looking For
Brain	Proper formation of brain structures, ventricle size
Heart	Four chambers, proper blood flow, valve function
Spine	Complete closure (ruling out spina bifida)
Kidneys	Both present and functioning
Stomach	Presence and normal appearance
Limbs	Proper development of arms, legs, hands, feet
Placenta	Position (checking for placenta previa)
Amniotic fluid	Adequate volume
Umbilical cord	Three vessels (two arteries, one vein)

The scan takes 30–45 minutes. If the sonographer can’t get clear views of all structures, you may be asked to return for a follow-up.

💡 Tip: If you want to know baby’s sex, the anatomy scan is usually when it can be reliably determined. Let your sonographer know your preference at the start of the appointment. The accuracy of sex determination at 20 weeks is approximately 99%, according to Ultrasound in Obstetrics & Gynecology journal.

Exercise in the Second Trimester

The second trimester is an excellent time to establish or maintain an exercise routine. ACOG recommends at least 150 minutes of moderate-intensity aerobic activity per week throughout pregnancy.

Safe Exercises

Exercise	Benefits	Precautions
Walking	Low impact, accessible anywhere	Stay hydrated; avoid extreme heat
Swimming	Supports joints, reduces swelling	Avoid diving; check pool water temperature
Prenatal yoga	Improves flexibility, reduces stress	Avoid hot yoga; skip deep twists
Stationary cycling	Cardiovascular fitness	Lower fall risk than outdoor cycling
Light strength training	Maintains muscle tone	Avoid lying flat on back after week 20

Exercises to Avoid

• Contact sports (soccer, basketball, martial arts)
• Activities with high fall risk (skiing, horseback riding, gymnastics)
• Scuba diving (decompression risk to baby)
• Hot yoga or hot tubs (overheating can harm fetal development)
• Exercises lying flat on your back for extended periods after week 20 (can compress a major vein)

⚠️ Important: Stop exercising and contact your provider if you experience vaginal bleeding, dizziness, chest pain, headache, calf swelling, or regular contractions during exercise.

Gestational Diabetes Screening

Between weeks 24 and 28, you’ll be offered the glucose challenge test (GCT) to screen for gestational diabetes, which affects 2–10% of pregnancies in the United States according to the CDC.

The Testing Process

Step 1 — Glucose Challenge Test (1-hour)

• Drink a 50g glucose solution
• Blood drawn after 1 hour
• If blood sugar is 140 mg/dL or higher, you proceed to step 2
• No fasting required

Step 2 — Glucose Tolerance Test (3-hour, if step 1 is elevated)

• Fast for 8–14 hours
• Fasting blood draw, then drink 100g glucose solution
• Blood drawn at 1, 2, and 3 hours
• Gestational diabetes is diagnosed if 2 or more values exceed thresholds

💡 Tip: Even if you feel fine, don’t skip the glucose test. Gestational diabetes often has no symptoms but can lead to complications including large birth weight (macrosomia), preterm birth, and preeclampsia if unmanaged.

Common Second Trimester Symptoms

Symptom	When It Starts	What Helps
Back pain	Weeks 14–16	Prenatal yoga, proper posture, pregnancy pillow
Round ligament pain	Weeks 14–20	Gentle stretching, changing positions slowly
Leg cramps	Weeks 16+	Stretching before bed, magnesium, hydration
Heartburn	Weeks 16+	Small meals, avoid lying down after eating, antacids (ask your provider)
Swollen feet	Weeks 20+	Elevate feet, compression socks, reduce sodium
Braxton Hicks	Weeks 20+	Rest, hydrate — they should stop (unlike real contractions)
Nasal congestion	Weeks 13+	Saline spray, humidifier; avoid decongestant sprays

Your Second Trimester Checklist

• ✅ Enjoy the return of energy — plan projects or a babymoon (ideal: weeks 14–28)
• ✅ Start wearing maternity clothes as needed
• ✅ Schedule the 20-week anatomy scan
• ✅ Begin feeling and tracking fetal movements
• ✅ Take the glucose challenge test (weeks 24–28)
• ✅ Start Kegel exercises for pelvic floor strength
• ✅ Research childbirth education classes
• ✅ Begin planning the nursery and baby registry
• ✅ Dental checkup (pregnancy hormones affect gum health)
• ✅ Discuss birth plan preferences with your provider
• ✅ Check your weight gain with our Weight Gain Calculator

FAQ

When will I feel the baby move?

Most first-time mothers feel fetal movements (quickening) between weeks 18 and 22. It may feel like flutters, gas bubbles, or gentle tapping. Women who have been pregnant before often notice movement earlier, around weeks 14–16. If you haven’t felt movement by week 24, mention it to your provider.

Is air travel safe during the second trimester?

Yes, the second trimester is generally the safest time to fly. Most airlines allow pregnant women to fly until 36 weeks. ACOG considers occasional air travel safe for women with uncomplicated pregnancies. Tips: walk the aisle hourly, stay hydrated, wear compression stockings, and choose an aisle seat for easy bathroom access.

Can I sleep on my back during the second trimester?

After week 20, ACOG recommends avoiding sleeping flat on your back for prolonged periods. The weight of the uterus can compress the inferior vena cava, reducing blood flow. Sleeping on your left side is ideal. A pregnancy pillow between your knees provides support and keeps you on your side.

How much weight should I gain in the second trimester?

According to ACOG, most of your pregnancy weight gain occurs in the second and third trimesters. For women with a normal pre-pregnancy BMI, that’s about 0.8–1 pound per week. The total recommended gain varies by BMI category — use our Weight Gain Calculator for personalized guidance.

References

• American College of Obstetricians and Gynecologists. “Exercise During Pregnancy.” acog.org
• American College of Obstetricians and Gynecologists. “Gestational Diabetes.” acog.org
• Centers for Disease Control and Prevention. “Gestational Diabetes.” cdc.gov
• Mayo Clinic. “Second Trimester Pregnancy.” mayoclinic.org
• National Institutes of Health. “Periviability.” nih.gov
• March of Dimes. “Your Baby’s Growth and Development.” marchofdimes.org